碳酸钾催化苯酚在超临界CO_2中合成水杨酸的实验研究

Synthesis of Salicylic Acid from Phenol Catalyzed by K_2CO_3 in Supercritical CO_2

在超临界CO2中以K2CO3为催化剂,由苯酚一步直接合成了水杨酸。改进了传统的有机酚酸（Kolbe-Schmitt反应）的两步法合成工艺。在CO2压力4~14 MPa、温度160~220℃,考察温度、压力、反应时间、催化剂用量等条件对水杨酸收率的影响。水杨酸最高得率接近54%,产物的选择性在99%以上,副产物有极少量对羟基苯甲酸。较为理想的反应条件为：反应温度190℃,反应压力8 MPa,反应时间3~5 h,催化剂用量10 mmol（nK2CO3/n phenol=1）。

The process of direct synthesis of salicylic acid from phenol catalyzed by K2CO3 in supercritical CO2 was studied.CO2 could act not only as a reagent but also as a solvent in this process.The conventional two-step synthesizing process of organic phenolic acid by Kolbe Schmitt reaction was improved,and the salicylic acid was synthesized by only one step.The influences of temperature（from 160 to 220℃）,pressure（from 4 to 14 MPa）,reaction time,amount of catalyst used were investigated.The highest salicylic acid yield could reach 54%,by-product is p-hydroxybenzoic acid of a very small amount,and selectivity is higher than 99%.The obtained optimum conditions of the reaction are as following： reaction temperature 190℃,reaction pressure 8 MPa,reaction time 3~5 h,amount of catalyst 10 mmol（n K2CO3/n phenol=1）.